class code1 {
        public int climbStairs(int n) {
                if(n == 1) return 1;

                int[] dp = new int[n+1];

                dp[1] = 1;
                dp[2] = 2;

                for(int i=3;i<=n;i++) {
                        dp[i] = dp[i-1] + dp[i-2];
                }

                return dp[n];
        }
}